My dad recently sent me a scanned photo from an old newspaper that he is using in a historical video he is working on. One of the main issues you face when working with projects of this nature is quality images. Sometimes, you have actual photos, which usually contain a workable amount of visual data to work with. Sometimes you’re on the other end of the spectrum with photocopies of old newspapers.

For this tutorial we’re looking at a pretty typical source image, a scan of a newspaper photo, and how to remove the halftone dot pattern caused by printing.

This image is of Frank Matty – for whom the hamlet of Mattydale, NY, north of Syracuse, is named. One of the only images available was from an old newspaper. Because we generally view newspapers from a comfortable distance, our minds ignore the dots that make up the photo so we can see the overall image without the distracting halftone.

However, when you scan in the image the halftone is much more noticeable – even more so when you use it in video.

Here are a couple of pretty easy steps you can take to eliminate much of the problem.

First of all, you need to know how you are going to use the final image (“begin with the end in mind”). In this case, we’re going to be using it in a video, so the end resolution will be either 72dpi for a static image or 150dpi, or so, to allow for zooms and pans, etc. For these samples, I am using a resolution of 72dpi.

The first thing you want to do is scan the newspaper in at a very high resolution. Here it was scanned at 600dpi. Sometimes you will want to scan the image at an angle to help avoid as much of a moire pattern as possible.

In Photoshop, I duplicated the layer and made it a Smart Object – not necessary to do both, perhaps, but I am always over-careful when working on a retouching job – so I could apply Smart Filters to it.

I added a Gaussian Blur of 3.7 pixels to essentially merge the dots and create smoother gradients. This amount may vary depending on the size of the dots and the resolution at which you scanned.

I then applied the Unsharp Mask filter with settings:

Amount: 120%

Radius: 5px

Threshold: 1 level
Applying too much sharpening will introduce halos around the edges which will take away from the impact of the image and will look very unprofessional in this usage.

Resample the image to your end resolution. The resampling will help remove some of the apparent blurriness of the image as well.

At the end, I just added a simple Curves Adjustment Layer to add some contrast.

The final shot, after those few quick steps, turned out pretty well.

Have you run into any issues when working with halftones? Got any tips that we might find useful here? Please share them in the comments so we can all get better results next time!

Thanks! This technique worked very well. I did some things different though: After I did the unsharp mask (without changing the threshold), I did a smart-sharpen and a reduce noise. The end result was incredible. I didn’t think it possible to do such a thing to the halftoned image.

I had an old scanner which had a setting called raster scan or interlace which was supposed to be used when copying halftones. It made excellent copies of newspaper photos. Unfortunately, the scanner wore out so I bought what I thought was a nice, modern scanner. Its help menu doesn’t even mention the problem!

No. The half-tone is from an image that has been printed with a process like they use for newspapers and when you scan it, it picks up the individual dots from the print. A moire pattern is similar – in that it can involve a half-tone pattern – but it is more from how the camera captures patterns in fabric, etc.

At the risk of seeming a little critical, Jason has come close, but still doesn’t quite have it. The phrase “how the camera captures patterns in fabric, etc.” while technically correct, still addresses the effect rather than the cause.

Moire patterns *can* occur when one dot pattern is superimposed over another. If the two dot patterns are defined with a different origin or are not aligned properly, the image passed through BOTH patterns is “shaded” where the patterns fail to match, and unaffected where the pattern elements are in close or exact alignment. If the patterns are the same dot shape, size, spacing, and angle, they can usually be aligned to cause their interferences to “disappear”, but working the one against the other, simply stated, can’t make the dots vanish, “as if by magic.”

The best (and most obvious) example I’ve ever seen of this effect occurred one day when I looked out through a screen-door where my Uncle Henry had stood up a window screen he had just repaired. Seeing my interest, he was willing to move around the window screen in front of the screen door, and turned it to change the angle of the one screen with respect to the other. The effect was to make the pattern very broad, or extremely tight. He didn’t know what it was called, but I remembered it vividly ten or so years later I ran across the topic in a high school physics class. He was pleased that I had remembered that spring day so long ago, and was pleased that I called and answered HIS question with, “It’s called a moire pattern, and here’s how it works . . .”

Thanks, by the way, for a really cool “recipe” on how to make them (appear) to disappear!

There is a better way of doing this but one has to work on the Fourier-transformed image. Any periodic pattern corrupting the original appears there as just a few isolated peaks of the amplitude. Removing them and inverse-transforming the image usually does much better job, especially if you can’t get the original in really high resolution or screen dots are too large to dissolve under a modest blur.
Free Fourier transform plug-ins used to be available on the net… or are they now standard in Photoshop?